1. Field of the Invention
The invention relates to an installation for extracting energy from a liquid in which swell occurs relative to a bottom.
Such an installation is particularly suitable for use in extracting energy from waves of water at sea.
2. Description of the Prior Art
It is known of waves at sea that they can occur in a wide range of amplitudes and frequencies. Extracting energy from swelling sea-water is of particular interest when the waves occurring in the-swelling water have been subjected to wind over very great distances (from hundreds to thousands of kilometers). Such waves may be present practically continuously at determined locations along a sea or ocean coast, wherein the wave length may amount to for instance 60 to 120 meters and the amplitude to for instance 1-3 meters.
It is generally known that variations in the pressure of swelling water decrease from the liquid surface in downward direction such that, at a depth corresponding with roughly half the wave length of the occurring waves, pressure variations are practically no longer detectable. This means that waves with a relatively small wave length have little influence on the dynamic hydrostatic pressure of the underlying water mass. Waves occurring during gales with a wave length of about 30 meters will for instance not penetrate to a depth further than about 15 meters. Pressure variations caused by a swelling water mass, wherein the wave length of the occurring waves amounts to for example about 130 meters will however be felt to a depth of about 65 meters.
It is an object of the invention to provide an installation of the type stated in the preamble, wherein the installation has a high performance, can extract energy from a swelling liquid with large wave lengths and can be placed on for instance the sea-bed.